Hilary Stout: On a Friday morning in October — Oct. 21, to be exact — Mark Trippetti, an advertising consultant from Williamsburg, Brooklyn, surrendered his laptop and iPhone to storage at a remote mountainside center in southern Colorado and prepared to drop out of human contact for a month.

The previous week he had begun the withdrawal process, leaving word with clients, cutting back his use of technology and giving up caffeine. Before checking out completely, he made one final call to his girlfriend, Jee Chang.

By careful design, Mr. Trippetti would not see or communicate with anyone until Nov. 20. At his spartan cabin …